Polarized plastic laminates are used for a variety of purposes including filters, optical elements, instrument display readout windows, sunglasses, and sport optical products, such as, ski goggles, motor cycle goggles, water sports goggles, and the like.
In the past, such laminates have comprised a cellulose acetate butyrate (CAB) outer sheet laminated to a polarizer comprising a thin film of stretched polyvinyl alcohol (PVA) dyed with an aqueous solution of iodine and potassium iodide or an organic dichroic dye, laminated to a CAB inner sheet, i.e., the laminates have comprised a polarizer sandwiched between two CAB sheets. The dyeing of the PVA sheet with iodine and potassium iodide or with an organic dichroic dye gives the sheet a neutral gray color. The thermoplastic CAB serves as a support for the thin fragile PVA polarizing element and thus allows it to be thermoformed into various curved shapes. Some polarized plastic laminates have used acrylic in place of one or both of the cellulose acetate butyrate sheets.
Although generally successfully, these products have suffered from some deficiencies. In particular, the products have lacked impact resistance which is clearly an important property for a product which is to be used in vigorous sports activities.
Also, the production of colored laminates has posed some problems. Polarized plastic laminates used in such applications as sunglass lenses, shields and ski goggles, need to be available in various colors in order to satisfy the requirement of different environmental viewing conditions and fashion demands.
In the past, colored polarized laminates have been produced by obtaining colored CAB support sheets and laminating those sheets to the gray PVA polarizing element thus resulting in a colored laminate. This method of producing colored polarized laminates has several major disadvantages. First, CAB is expensive and requires long lead times and large quantity purchases. Further, CAB is not available in all colors and custom color formulations are difficult to make, expensive, and again require long lead times. Long lead times are an especially significant problem in the field of fashion eyewear, where the successful producer of laminates must respond quickly to market and fashion changes which may only last for a single season. Colored polarized plastic laminates using CAB have had a difficult time meeting the color and timing requirements of this important market.
The present invention is designed to overcome both the impact and coloring deficiencies of prior art polarized plastic laminates.